Such a beating apparatus is known from SE-B-307 504, wherein the rotor is a drum, the inlet for suspension opens into the drum, a plurality of stator shoes is arranged at the outer periphery of the drum and a space outside the drum communicates with the outlet. The drum is open towards the inlet and a stationary distributor drum is inserted in the drum to direct incoming flow of suspension towards predetermined locations of the internal periphery of the drum, viz., those locations located in the beginning, as counted in the rotational direction of the drum, of the stator shoes arranged at the outer periphery of the drum. From strength reasons, however, a drum for a beating apparatus of this kind must be provided with a relatively thick envelope wall. This, in turn, results in that the perforations of the envelope wall become so extended in the radial direction that the passage time for a fibre from entering a perforation until leaving it may be so long that the fibre leaves a perforation only after it has passed a stator shoe, i.e., between two stator shoes, which results in that the unbeaten fibres mixes outside the rotor with beaten fibres having passed through the stator shoes. This, of course, results in an insufficient beating of the suspension.